Accented Models: Evaluating their effectiveness in Building Energy Simulation

This report examines the effectiveness of the accented modeling method for building energy simulation. The traditional full-zone modeling method is too time consuming and in some cases unnecessary, so a more efficient building modeling method – accented modeling is introduced. The purpose of this research is to analyze if, and under what conditions, an accented building model is an effective representation of the actual building. By using DesignBuilder and EnergyPlus as software packages for model development and simulation, two building models for the Lofts on the Washington University campus in St. Louis, MO were created for comparison—a full-zone model and an accented model. This report first examines the accuracy of the full-zone model, and then, by comparing the accurate full-zone model to the accented model, shows that the accented modeling method is effective in this case

Aerodynamic Study of Stability and Control of Straight Flying-Wings

The bell-spanload, or bell-shaped lift distribution, gives proverse yaw for outer aileron deflections, a key factor in controlling a tailless vehicle. Study of bell-spanload applications have been limited to swept wings with elevon control schemes, relying on a well-tuned proverse yaw response for a differential elevon deflection. In examining unswept wings, symmetric outer control surface deflections have minimal associated pitching moment, allowing their use in adjusting the lift distribution to optimize for a wide range of flight conditions. Lateral-directional control of bell-spanloads can be improved by the use of an additional set of ailerons inboard of the mid-span vortices. The inboard ailerons provide traditional adverse yaw which serves as a linearly independent control vector relative to the existing proverse yaw outer surfaces; the two vectors are sufficient to define a parallelogram-shaped controllable region in the roll-yaw control space

Numerical Simulation of Chemical Looping and Calcium Looping Combustion Processes for Carbon Capture

Efficient carbon capture and storage (CCS) technologies are needed to address the rising carbon emissions from power generation using fossil fuels that have been linked to global warming and climate change. Chemical looping combustion (CLC) is one such technology that has shown great promise due to its potential for high-purity carbon capture at low cost. Another CCS technology that has garnered interest in recent years is calcium looping (CaL), which utilizes calcium oxide and the carbonation-calcination equilibrium reactions to capture CO2 from the flue stream of fossil fuel power plants. Computational fluid dynamics (CFD) simulations of two CLC reactors are presented in this chapter, along with system level simulations of CaL for postcombustion carbon capture. CFD simulation of a CLC reactor based on a dual fluidized bed reactor is developed using the Eulerian approach to characterize the chemical reactions in the system. The solid phase consists of a Fe-based oxygen carrier while the gaseous fuel used is syngas. Later, the detailed hydrodynamics in a CLC system designed for solid coal fuel is presented based on a cold flow experimental setup at National Energy Technology Laboratory using the Lagrangian particle-tracking method. The process simulation of CaL using Aspen Plus shows an increasing marginal energy penalty associated with an increase in the CO2 capture efficiency, which suggests a limit on the maximum carbon capture efficiency in practical applications of CaL before the energy penalty becomes too large

Computational Fluid Dynamics Study on the Effect of Using an Under-Tray Addition to Motorsport

The aim of this study is to study the effect of deploying an under-tray to a Formula Society of Automotive Engineers (FSAE) racecar for the Washington University FSAE racing team (WashU Racing) through Computational Fluid Dynamics (CFD). The under-tray geometry was developed to cover the bottom of an FSAE racecar by members of the WashU Racing team (a college FSAE team). The under-tray was added to the existing geometry of the Formula racecar; a mesh around it was then generated using the mesh generator in ANSYS and CFD simulations were performed using ANSYS Fluent to determine lift and drag values for the car in the presence of under-tray. Processing of numerical data was done using ANSYS EnSight. The center of pressure of the car was found analytically. All physical quantities obtained with inclusion of under-tray were compared to those obtained for the model of the car without the under-tray. It was found that under-tray slightly increases the lift coefficient and significantly decreases the drag coefficient. The study shows that the inclusion of an under-tray would be a worthwhile addition to the FSAE car

CFD Study of Wake Interactions from Multiple Vertical Axis Wind Turbines using Actuator Cylinder Theory

This paper studies the flow field and power generation from Vertical Axis Wind Turbine (VAWT) arrays using an extension of the Actuator Cylinder Model that includes the viscous effects. The ideal spacing for two VAWT arrays is determined by solving the Reynolds-Averaged Navier Stokes (RANS) equations with the Spalart-Allmaras (SA) turbulence model in ANSYS Fluent. Next, a third VAWT is introduced downfield and calculations are repeated to determine the ideal downfield distance for each spacing variation of the leading row of two turbines. Comparisons are made with an isolated vertical axis wind turbine. Differences in generated power are discussed

Computational Fluid Dynamics Analysis of High Lift, Inverted Airfoils in Ground Effect

Formula SAE vehicles are formula styled (open-wheeled and open cockpit) racecars that are designed to race on an autocross circuit. Highly competitive vehicles in the competition implement aerodynamic devices, which generate negative lift for the vehicle. This negative lift, or downforce, increases the amount of traction between the racecar’s tires and the ground that ultimately allows drivers to turn at faster speeds. Commonly used aerodynamic devices are a front and rear wing; the wing cross sections are defined by configurations of multiple 2D airfoils. This paper focuses on the systematic design of a Formula SAE specific front wing through the comparisons of high lift, inverted airfoils, in ground effect in order to maximize the negative lift coefficient. Five selected high lift, single element airfoils are iterated through multiple angles of attack and the three superior airfoils are iterated through a second study of height off the ground. A third study begins to look at combining the single airfoils into a two element airfoil configuration to further increase negative lift generation

Validation and Optimization of Ptera Software: An Open-Source Unsteady Simulator for Flapping Wings

Scientists have long used the unsteady vortex lattice method (UVLM) to simulate flapping-wing flight. However, there are few open-source UVLM solvers designed for research in this field. The newly released Ptera Software is, to the best of the authors’ knowledge, the only open-source UVLM solver for flapping wings that is in active development. This report documents the next steps in Ptera Software’s progress: the validation of its results and the optimization of its performance. Comparing Ptera Software’s output to high-fidelity experimental data of the pressures on a flapping-wing robot shows that the simulated results predict the trends and magnitudes of the net lift over time with reasonable accuracy. Also, by using several computational methods, the researchers optimized the source code such that the solver’s latest iteration is over three times faster than previous versions. The present results demonstrate that Ptera Software correctly implements the UVLM and can simulate flapping-wing flight with reasonable accuracy under this method’s assumptions. Additionally, it is now fast enough for use as an iterative tool in the design of novel flapping-wing micro aerial vehicles (FWMAVs)